Reactor neutrino experiments have seen major improvements in precision in recent years. With the experimental uncertainties becoming lower than those from theory, carefully considering all sources of ...ν¯e is important when making theoretical predictions. One source of ν¯e that is often neglected arises from the irradiation of the nonfuel materials in reactors. The ν¯e rates and energies from these sources vary widely based on the reactor type, configuration, and sampling stage during the reactor cycle and have to be carefully considered for each experiment independently. In this article, we present a formalism for selecting the possible ν¯e sources arising from the neutron captures on reactor and target materials. We apply this formalism to the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory, the ν¯e source for the the Precision Reactor Oscillation and Spectrum Measurement (PROSPECT) experiment. Overall, we observe that the nonfuel ν¯e contributions from HFIR to PROSPECT amount to 1% above the inverse β decay threshold with a maximum contribution of 9% in the 1.8–2.0 MeV range. Nonfuel contributions can be particularly high for research reactors like HFIR because of the choice of structural and reflector material in addition to the intentional irradiation of target material for isotope production. We show that typical commercial pressurized water reactors fueled with low-enriched uranium will have significantly smaller nonfuel ν¯e contribution.
The Precision Reactor Oscillation and Spectrum (PROSPECT) Experiment is a reactor neutrino experiment designed to search for sterile neutrinos with a mass on the order of 1 eV/c2 and to measure the ...spectrum of electron antineutrinos from a highly-enriched 235U nuclear reactor. The PROSPECT detector consists of an 11 by 14 array of optical segments in 6Li-loaded liquid scintillator at the High Flux Isotope Reactor in Oak Ridge National Laboratory. Antineutrino events are identified via inverse beta decay and read out by photomultiplier tubes located at the ends of each segment. The detector response is characterized using a radioactive source calibration system. This paper describes the design, operation, and performance of the PROSPECT source calibration system.
Reactor neutrino experiments have seen major improvements in precision in recent years. With the experimental uncertainties becoming lower than those from theory, carefully considering all sources of
...is important when making theoretical predictions. One source of
that is often neglected arises from the irradiation of the nonfuel materials in reactors. The
rates and energies from these sources vary widely based on the reactor type, configuration, and sampling stage during the reactor cycle and have to be carefully considered for each experiment independently. In this article, we present a formalism for selecting the possible
sources arising from the neutron captures on reactor and target materials. We apply this formalism to the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory, the
source for the the Precision Reactor Oscillation and Spectrum Measurement (PROSPECT) experiment. Overall, we observe that the nonfuel
contributions from HFIR to PROSPECT amount to 1% above the inverse beta decay threshold with a maximum contribution of 9% in the 1.8-2.0 MeV range. Nonfuel contributions can be particularly high for research reactors like HFIR because of the choice of structural and reflector material in addition to the intentional irradiation of target material for isotope production. We show that typical commercial pressurized water reactors fueled with low-enriched uranium will have significantly smaller nonfuel
contribution.
Using the entire sample of 467 × 10 6 Υ ( 4 S ) → B ¯¯¯ B decays collected with the BABAR detector at the PEP-II asymmetric-energy B factory at the SLAC National Accelerator Laboratory, we perform an ...analysis of B ± → D K ± decays, using decay modes in which the neutral D meson decays to either C P -eigenstates or non- C P -eigenstates. We measure the partial decay rate charge asymmetries for C P -even and C P -odd D final states to be A C P + = 0.25 ± 0.06 ± 0.02 and A C P − = − 0.09 ± 0.07 ± 0.02 , respectively, where the first error is the statistical and the second is the systematic uncertainty. The parameter A C P + is different from zero with a significance of 3.6 standard deviations, constituting evidence for direct C P violation. We also measure the ratios of the charged-averaged B partial decay rates in C P and non- C P decays, R C P + = 1.18 ± 0.09 ± 0.05 and R C P − = 1.07 ± 0.08 ± 0.04 . We infer frequentist confidence intervals for the angle γ of the unitarity triangle, for the strong phase difference δ B , and for the amplitude ratio r B , which are related to the B − → D K − decay amplitude by r B e i ( δ B − γ ) = A ( B − → ¯¯¯ D 0 K − ) / A ( B − → D 0 K − ) . Including statistical and systematic uncertainties, we obtain 0.24 < r B < 0.45 ( 0.06 < r B < 0.51 ) and, modulo 180°, 11.3 ° < γ < 22.7 ° or 80.8 ° < γ < 99.2 ° or 157.3 ° < γ < 168.7 ° ( 7.0 ° < γ < 173.0 ° ) at the 68% (95%) confidence level.
Reactor neutrino experiments have seen major improvements in precision in recent years. With the experimental uncertainties becoming lower than those from theory, carefully considering all sources of ...¯νe is important when making theoretical predictions. One source of ¯νe that is often neglected arises from the irradiation of the nonfuel materials in reactors. The ¯νe rates and energies from these sources vary widely based on the reactor type, configuration, and sampling stage during the reactor cycle and have to be carefully considered for each experiment independently. In this article, we present a formalism for selecting the possible ¯νe sources arising from the neutron captures on reactor and target materials. We apply this formalism to the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory, the ¯νe source for the the Precision Reactor Oscillation and Spectrum Measurement (PROSPECT) experiment. Overall, we observe that the nonfuel ¯νe contributions from HFIR to PROSPECT amount to 1% above the inverse β decay threshold with a maximum contribution of 9% in the 1.8–2.0 MeV range. Nonfuel contributions can be particularly high for research reactors like HFIR because of the choice of structural and reflector material in addition to the intentional irradiation of target material for isotope production. We show that typical commercial pressurized water reactors fueled with low-enriched uranium will have significantly smaller nonfuel ¯νe contribution.
We present improved measurements of the branching fraction B , the longitudinal polarization fraction f L , and the direct C P asymmetry A C P in the B meson decay channel B + → ρ + ρ 0 . The data ...sample was collected with the BABAR detector at SLAC. The results are B ( B + → ρ + ρ 0 ) = ( 23.7 ± 1.4 ± 1.4 ) × 10 − 6 , f L = 0.950 ± 0.015 ± 0.006 , and A C P = − 0.054 ± 0.055 ± 0.010 , where the uncertainties are statistical and systematic, respectively. Based on these results, we perform an isospin analysis and determine the Cabibbo-Kobayashi-Maskawa phase angle α = arg ( − V t d V ∗ t b / V u d V ∗ u b ) to be ( 92.4 + 6.0 − 6.5 ) ° .
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